the story didn’t happen yet.
Ok...?
it was released in july 1985 but marty goes back in time in october
True. Apparently it's because they thought it would be in cinemas in October but the test screenings were so successful that the studio wanted the release date brought forward so it would be screened through summer.
that makes sense.
I just don't see how this matters in the least.
And neither did Star Trek or any other story that takes place in the future.